(1) Field of the Invention
The present invention relates to an optical wave guide element wherein an optical wave guide is formed on a substrate having the electro-optic effect and the manufacture of the same, in particular, to an optical wave guide element characterized by the connection structure of a substrate having the electro-optic effect to optical fiber and the manufacture of the same.
(2) Related Art Statement
A dense wavelength division multiplexing (DWDM) technology has been developed for optical communication systems corresponding to an increase in the demand for high speed, large capacity data communication systems in recent years. As a result, it becomes necessary to utilize the systems by combining a great number of optical wave guide elements, such as optical modulators, and in particular, miniaturization of the bodies of these optical wave guide elements and the connection structures of the bodies to optical fiber is required for making the entirety compact, so as to prevent the entire device from increasing in size.
An optical wave guide, within an optical wave guide element that forms an optical modulator, and optical fiber, for incoming and outgoing radiation connected to the optical wave guide, are aligned in an optical modulator module (which is formed of a metal case containing the body of an optical modulator and parts attached to this, for easy handling) according to the prior art. As a result, in the case where the optical modulator module is contained in the device box, as shown in FIG. 1, the shortest possible length of the system is the sum of the minimum curvature length (section R of FIG. 1) of optical fiber 3 extending from the case of optical modulator module 1 and the length L of the case (strictly speaking, lengths l1 and l2 of support members 4 and 5, for supporting optical fiber extending from the case, should also be added to the above sum).
As a result, in order to reduce the length of the system containing the optical modulator module, as shown in FIG. 2, it becomes necessary to arbitrarily set the angle between optical fiber for incoming radiation and optical fiber for outgoing radiation which extend from the optical modulator module so that the system can be bent 90°, for example, eliminating the minimum curvature length (section R) of the optical fiber.
Here, 6, shown in FIGS. 1 and 2, indicates terminals which allow the input of a signal voltage of a microwave and the output of a detection signal from a light receiving element contained in optical modulator module 1. In addition, in order to reduce optical loss in the connection between the optical modulator and the optical fiber, as shown in FIGS. 1 and 2, the connection between the optical modulator and the optical fiber has an inclination of approximately 2°.
As shown in FIG. 2, in order to bend the optical fiber for incoming radiation 90°, (1) a method for bending the optical fiber 90° within the case of optical modulator module 1 (Japanese Unexamined Patent Publication H7(1995)-294781), (2) a method for bending the optical axis of incoming light into or outgoing light from the optical wave guide element 90° by using a reflective member such as a prism (Japanese Unexamined Patent Publication 2001-242338), and the like, have been proposed.
When method (1) is used, however, it becomes necessary to additionally secure a space to contain the optical fiber that has been bent 90° inside the case, causing the length L′ of the case to be extended. Furthermore, when method (2) is used, the length L′ of the case becomes long in the same manner as in method (1) in order to secure the space for containing the reflective member, and in addition, the manufacturing process becomes complicated because the optical positions must be adjusted and, therefore, method (2) is defective in that manufacturing becomes difficult.
An object of the present invention is to solve the above described problem, and to provide an optical wave guide element for making the miniaturization of the entire device including the optical wave guide element possible, by connecting optical fiber for incoming and outgoing radiation to the optical wave guide element, so that the optical wave guide element and the optical fiber are positioned at an angle of approximately 90°, as well as to provide a manufacturing method for the same.